Stepper motor with a rotor teeth sensor

Claim 1

A brushless motor comprising: a rotor core formed of a magnetic material having magnetic pole teeth at a uniform angular pitch, a stator core formed of a magnetic material, having a plural number n of magnetic pole teeth which face said rotor core across an air gap, said stator core magnetic pole teeth having a same angular pitch as the angular pitch of said rotor core magnetic pole teeth, a plurality of n phase coils provided on said stator core, energization of which causes magnetic attraction and repulsion between said rotor core and said stator core; bearing means for rotatably supporting said rotor core so that said air gap between said rotor core and said stator core remains substantially constant; and rotor teeth position sensor means located adjacent said rotor core for detecting a passage of said rotor magnetic pole teeth and issuing n phase electric conducting control signals to generate substantially sine-shaped output signals, each phase of said n phase signals being generated when said rotor teeth sensor means detects particular pole teeth and for supplying said n phase signals to said n phase coils to respectively energize each of said n phase coils at an appropriate time as indicated by said rotor position, detected by said rotor teeth position sensor means.